According to the classical theory of interest, which long served as a framework for the theory of money, prices, and income, the rate of interest is determined by the supply of and demand for savings. Monetary theorists, such as Wicksell, Fisher, Hawtrey, and Keynes, erected an imposing edifice on this foundation. Then came the Great Depression and disillusionment, the Second World War and the pegged market régime. At the same time, a growing ferment in the literature undermined the classical foundations. With regard to the savings function, agnosticism prevailed. As for investment demand, empirical studies and theoretical developments alike relegated the rate of interest to a minor role in entrepreneurial decision-making. In deference to considerations of debt management, open market operations were held in abeyance. Thus, little was to be expected of quantitative credit control as an instrument of public policy in the post-war period.